Honeybee Counter - I designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive. The low power circuit uses a slotted opto-sensor to detect the passing bees. The circuit advances an electronic counting. . . Circuit by David A. Johnson P.E.-July, 2000

Indicates when it is Time to Dust - I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough. I have not yet built and tested this circuit completely but in concept it should work. . . Circuit by David Johnson P.E.-June, 2000

Indicates when it is Time to Dust - I have used the circuit below for many different applications, which require ultra low power drain. It uses a single CA4013 flip/flop. One section forms a pulse generator. The generator produces 100uS pulses at a rate of about 1 per secondCircuit Solution by David Johnson P.E.-May, 2006

LED Flashing Badge #1 - I have seen numerous flashing light badges at trade shows and conventions. They are often handed out as gifts to promote some business. The devices often use inefficient circuits, which cause the battery power source to be quickly depleted. . . Circuit by David Johnson P.E.-March, 2002

LED Flashing Badge #2 - This circuit uses a CD4013 dual D Flip/Flop IC. A single lithium battery will provide months of continuous LED flashing. It also has a tiny push-button switch to turn on and off the light flashing. . . Circuit by David A. Johnson P.E.-March, 2002

Miniature Pushbutton On/Off Switch - In many battery powered devices, you would like to turn the circuit on and off by pressing a small pushbutton switch. One press turns the device on and second press turns it back off. The flip/flop circuit below uses a minimum number of parts to perform . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

On/Off Flip/Flop Circuit with Automatic Timeout - This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time. With the components shown, the output will stay on for only about 20 seconds. . . Circuit by Dave Johnson P.E.-May, 2012

One Shot (D-Flip/Flop) Circuit - Yes you can use cheap D flip/flop logic circuits as nice one-shot pulse generators. This schematic shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds. . . Circuit by David A. Johnson P.E.-June, 2000

Oneshot & Latch Pushbutton - This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean pulse or a sustained push on-push off signal. It can operate from 3v to 18v . . . Hobby Circuit designed by David Johnson P.E.-March, 2002

Gated Oscillator Emulates a Flip-Flop - 03/16/95 EDN Design Ideas: The gated oscillator in Fig 1 holds its existing state when disabled rather than being forced high or low-a singular property. Further, you can generate an output at one-half the input frequency if you choose R1 and C so that the oscillator changes state just once when its input goes high. This configuration eliminates a flip-flop. __ Circuit Design by Einar Abell, ADA Instruments, Three Rivers, CA

Generate Short Delayed Pulse - This circuit generates a short 10ms pulse 15 minutes after a start pushbutton switch is activated . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Generator has independent pulse width, frequency - 11/11/99 - EDN Design Ideas: A common circuit in electronics is the square-wave, astable multivibrator (one-shot) , which is useful for various purposes, such as timing circuits and audible alarms. The most common way to generate the desired square wave is to use the inexpensive 555 timer. The need sometimes arises for a square wave with fixed frequency but variable pulse width or vice versa. __ Circuit Design by Davinder Oberoi

High-Speed Pulse Generator Has Programmable Levels - 12/31/69 EDN Design Ideas: Lilliputian dimensions associated with the submicron geometries of most digital and many analog processes result in much faster circuit operation. As ICs speed up, the rise and fall times of most pulse and function generators, which are typically 5 nsec, become inadequate for measuring time intervals lower than 20 nsec. You can overcome this limitation with analog comparators or advanced CMOS
logic gates, which create faster digital edges. __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

High-Speed Pulse Modulator Retains Signal Envelope - 06-Aug-09 EDN Design Ideas: Modulated signals have the ac components they need to pass through transformers. - The circuit in Figure 1 enables you to convert an arbitrary, relatively slowly varying voltage waveform to a new waveform in which the instantaneous values of the original waveform alternate with positive and negative signs. The new waveform retains information about the original waveform, . __ Circuit Design by MariĆ”n Stofka, Slovak University of Technology, Bratislava, Slovakia

High-Voltage DC Generator - Voltage, by definition, is the electrical pressure that causes current to flow through a conductor. When that pressure is sufficiently high, a high voltage is produced. But how do we define high-voltage? is 100, 1000, or 10, 000 volts considered high voltage? When compared to 10 volts, they all can be considered high voltage __ Designed by Tony van Roon VA3AVR

Honeybee Counter - i designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive. The low power circuit uses a slotted opto-sensor to detect the passing bees. The circuit advances an electronic counting. . . Circuit by David A. Johnson P.E.-July, 2000

LED Flashing Badge #1 - i have seen numerous flashing light badges at trade shows and conventions. They are often handed out as gifts to promote some business. The devices often use inefficient circuits, which cause the battery power source to be quickly depleted. . . Circuit by David Johnson P.E.-March, 2002

LED Flashing Badge #2 - This circuit uses a CD4013 dual D Flip/Flop iC. A single lithium battery will provide months of continuous LED flashing. it also has a tiny push-button switch to turn on and off the light flashing. . . Circuit by David A. Johnson P.E.-March, 2002

Miniature Pushbutton On/Off Switch - in many battery powered devices, you would like to turn the circuit on and off by pressing a small pushbutton switch. One press turns the device on and second press turns it back off. The flip/flop circuit below uses a minimum number of parts to perform . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Minimize the Short-Circuit Current Pulse in a Hot-Swap Controller - 27-May-04 EDN Design Ideas: Because of internal circuit-breaker delay and limited MOS-gate pulldown current, many hot-swap controllers do not limit current during the first 10 to 50 µsec following a shorted output. The result can be a brief flow of several hundred amperes. A simple external circuit can counter this problem by minimizing the initial current spike and terminating the short circuit within 200 to 500 nsec __ Circuit Design by Jim Sherwin and Thong Huynh, Maxim Integrated Products, Sunnyvale, CA

Monostable Flip Flops (One Shot) - The two circuits below illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period. For shorter periods __ Designed by Bill Bowden

Multiple Pulse Generator - i used this circuit to ring my doorbell rapidly three times when a car pulled into my driveway. R2 and C2 set the output frequency. Use a diode and resistor to change the duty cycle, if desired. R1 and C1 set the cycle time which sets the number of pulse __ Designed by Andrew R. Morris

On/Off Flip/Flop Circuit with Automatic Timeout - This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time. With the components shown, the output will stay on for only about 20 seconds. . . Circuit by Dave Johnson P.E.-May, 2012

One Hz Pulse Frequency Generator - Here is a 1Hz pulse/frequency generator using the popular timer IC 555 which is wired as an Astable Multivibrator. The output pulses can be indicated visually by the LED. An Astable Multivibrator, often called a free-running Multivibrator, is a rectangular-wave generating circuit. Unlike the Monostable Multivibrator, this __ Designed by D Mohankumar

One Shot (D-Flip/Flop) Circuit - Yes you can use cheap D flip/flop logic circuits as nice one-shot pulse generators. This schematic shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds. . . Circuit by David A. Johnson P.E.-June, 2000

Oneshot & Latch Pushbutton - This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean pulse or a sustained push on-push off signal. it can operate from 3v to 18v . . . Hobby Circuit designed by David Johnson P.E.-March, 2002

Op Amp as a Set/Reset Flip-Flop - 05/24/12 EDN Design Ideas: Eliminate a flip-flop package by using a spare op amp for an SR latch function. You can make a set/reset flip-flop from two NAND or NOR gates or use readily available set/reset flip-flop iCs, such as the 74HC279 quad-set/reset latch. The drawback of these methods is that they require a large amount of space to form the flip-flop. Even if you need only one flip-flop, you must use a large IC package with this approach. However, you can use a spare rail-to-rail op amp to perform the needed latch function (Figure 1). __ Circuit Design by Aruna Rubasinghe